Helicase (nsP13) protein is a crucial component required for virus replication in host cells and could serve as a feasible target for anti-MERS and anti-SARS chemical therapies, the review authors wrote, citing as an example, the recent development of a small 1,2,4-triazole derivative that inhibited the viral NTPase/helicase of SARS- and MERS-CoVs and demonstrated high antiviral activity and low cytotoxicity.
Membrane-bound viral RNA synthesis inhibitors
Antiviral agents that target membrane-bound coronaviral RNA synthesis represent a novel and attractive approach, according to Dr. Pillaiyar and colleagues. And recently, an inhibitor was developed that targets membrane-bound coronaviral RNA synthesis and “showed potent antiviral activity of MERS-CoV infection with remarkable efficacy.”
Host-based, anti-CoV treatment options
An alternate therapeutic tactic is to bolster host defenses or to modify host susceptibilities to prevent virus infection or replication. The innate interferon response of the host is crucial for the control of viral replication after infection, and the addition of exogenous recombinant interferon or use of drugs to stimulate the normal host interferon response are both potential therapeutic avenues. For example, nitazoxanide is a potent type I interferon inducer that has been used in humans for parasitic infections, and a synthetic nitrothiazolyl-salicylamide derivative was found to exhibit broad-spectrum antiviral activities against RNA and DNA viruses, including some coronaviruses.
Numerous other host pathways are being investigated as potential areas to enhance defense against infection and replication, for example, using inhibitors to block nucleic acid synthesis has been shown to provide broad-spectrum activity against SARS-CoV and MERS-CoV.
One particular example is remdesivir, a novel nucleotide analog antiviral drug, that was developed as a therapy for Ebola virus disease and Marburg virus infections. It was later shown to provide “reasonable antiviral activity against more distantly related viruses, such as respiratory syncytial virus, Junin virus, Lassa fever virus, and MERS-CoV,” the authors wrote.
Also of interest regarding remdesivir’s potential broad-spectrum use is that it has shown potent in vitro “antiviral activity against Malaysian and Bangladesh genotypes of Nipah virus (an RNA virus, although not a coronavirus, that infects both humans and animals) and reduced replication of Malaysian Nipah virus in primary human lung microvascular endothelial cells by more than four orders of magnitude,” Dr. Pillaiyar and colleagues added. Of particular note, all remdesivir-treated, Nipah virus–infected animals “survived the lethal challenge, indicating that remdesivir represents a promising antiviral treatment.”
In a press briefing earlier this month, Anthony S. Fauci, MD, director of the National Institute of Allergy and Infectious Diseases, reported that a randomized, controlled, phase 3 trial of the antiviral drug remdesivir is currently underway in China to establish whether the drug would be an effective and safe treatment for adults patients with mild or moderate 2019 Novel Coronavirus (2019-nCoV) disease.
“Our increasing understanding of novel emerging coronaviruses will be accompanied by increasing opportunities for the reasonable design of therapeutics. Importantly, understanding this basic information about CoV protease targets will not only aid the public health against SARS-CoV and MERS-CoV but also help in advance to target new coronaviruses that might emerge in the future,” the authors concluded.
Dr. Pillaiyar and colleagues reported that they had no financial conflicts of interest.
SOURCE: Pillaiyar T et al. Drug Discov Today. 2020 Jan 30. .